Polyurethane and water-compatible polyurethane resin

ABSTRACT

The present invention provides a polyurethane exhibiting a superior adhesive property, bonding property, weather resistance, water resistance, and the like, and comprising in a molecule: an acidic group which is neutralized by a basic compound; and a structural unit represented by general formula (I):(in the formula, R&lt;1 &gt;and R&lt;2 &gt;are identical or different, and represent a lower alkyl group).

TECHNICAL FIELD

The present invention relates to aqueous polyurethane resins exhibitinga superior adhesive property, bonding property, weather resistance,water resistance, and the like, and polyurethanes for use in theseresins.

BACKGROUND ART

Aqueous polyurethane resins are widely employed as resins for use incoating materials, adhesives, binders, inks, or the like since theyexhibit superior dynamically physical properties, abrasion resistance,flexibility, and the like. In particular, there is a recent trend forrestricting the discharge of organic solvents to the atmosphere in viewof the environmental protection of the earth, and for this reason, inthe future, applications of aqueous polyurethane resins may be broadenedin various uses.

As aqueous polyurethane resins, those prepared from a diol having anacidic group such as dimethylol propionic acid, dimethylol butanoicacid, or the like as a raw material, and the acidic group of which isneutralized by a base are known (Japanese Examined Patent Application,Second Publication No. Sho 61-5485, Japanese Examined PatentApplication, Second Publication No. Hei 4-488, Japanese UnexaminedPatent Application, First Publication No. Hei 8-27242, and JapaneseUnexamined Patent Application, First Publication No. Hei 6-329744).

For the case where aqueous polyurethane resins are employed for use incoating materials, adhesives, or the like, they are required to exhibitcharacteristics of maintaining physical properties for a long period oftime, such as weather resistance, water resistance, and the like, aswell as to exhibit a superior adhesive property and bonding property.However, the aqueous polyurethane resins disclosed in the publicationsdescribed above cannot practically meet the performance requirements.

In addition, WO96/09334 discloses polyurethanes employing2,4-diethyl-1,5-pentanediol. The polyurethanes disclosed in the Examplesof said publication cannot form an aqueous polyurethane resin due totheir low solubility in water or the like.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide an aqueous polyurethaneresins exhibiting a superior adhesive property, bonding property,weather resistance, water resistance, and the like, and to providepolyurethanes employed in said resins.

That is, the present invention provides polyurethanes comprising in amolecule: an acidic group which is neutralized by a basic compound; anda structural unit represented by general formula (I):

(in the formula, R¹ and R² are identical or different, and represent alower alkyl group).

In addition, the present invention provides an aqueous polyurethaneresins comprising said polyurethane.

In the definition of the groups of general formula (I), examples of thelower alkyl groups include straight or branched alkyl groups having 1 to8 carbon atoms, such as a methyl group, an ethyl group, a propyl group,an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group,a tert-butyl group, a pentyl group, an isoamyl group, a neopentyl group,a 2-pentyl group, a 3-pentyl group, a hexyl group, a heptyl group, anoctyl group, and the like.

In addition, examples of the acidic groups include a carboxyl group, asulfo group, a phosphono group, and the like. Among these, a carboxylgroup is preferable.

Examples of the basic compounds for neutralizing the acidic groupinclude the basic compounds described below.

The polyurethanes of the present invention can be synthesized accordingto known methods (Japanese Unexamined Patent Application, FirstPublication No. Hei 8-27242, Japanese Unexamined Patent Application,First Publication No. Hei 8-259884, or the like).

One example of the methods for preparing a polyurethane of the presentinvention is explained in (1) to (3) below.

(1) Preparation of a polyester polyol: 2,4-Dialkyl-1,5-pentanediol whichis a diol comprising a structural unit in a molecule, the unitrepresented by general formula (I), is reacted with a dicarboxylic acidto produce a polyester polyol.

(2) Preparation of a urethane prepolymer and neutralization of the same:The above polyester polyol, a compound having an acidic group, and apolyisocyanate are reacted to produce a urethane prepolymer having anisocyanate group at the terminal. Then, the acidic group of the aboveurethane prepolymer is neutralized by a basic compound.

(3) Preparation of a polyurethane: The above urethane prepolymer,wherein the acidic group is neutralized, is reacted with achain-elongation agent to produce a polyurethane according to thepresent invention.

In the following, steps (1) to (3) are explained in more detail.

(1) Preparation of the Polyester Polyol:

A polyester polyol can be obtained from 2,4-dialkyl-1,5-pentanediol anda dicarboxylic acid according to a known method (such as that describedin Japanese Unexamined Patent Application, First Publication No. Sho48-101496, WO98/44014, WO99/06498, or the like) by, for example, heatingthem, or heating them under reduced pressure, followed by dehydrationpolycondensation.

Examples of the dicarboxylic acids include succinic acid, adipic acid,azelaic acid, sebacic acid, maleic acid, fumaric acid, phthalic acid,and the like. They can be employed alone or in combination with two ormore of the same. In addition, instead of the dicarboxylic acid, an acidanhydride of the dicarboxylic acid or a lower alkyl ester of thedicarboxylic acid, such as a methyl ester, an ethyl ester, or the like,may be employed.

2,4-Dialkyl-1,5-pentanediol can be prepared according to a methoddescribed in WO97/19904, or alternatively is commercially available.

Furthermore, in addition to 2,4-dialkyl-1,5-pentanediol, other diols maybe simultaneously employed. In this case, the ratio of2,4-dialkyl-1,5-pentanediol to the total of the diols is preferably 30%by weight or more, and more preferably is 40% by weight or more.

Examples of the other diols which can be simultaneously employed includeethylene glycol, propylene glycol, 1,4-butanediol, diethylene glycol,1,6-hexanediol, 2-butyl-2-ethyl-1,3-propanediol,3-methyl-1,5-pentanediol, 1,4-bis(β-hydroxyethoxy)benzene, and the like.In the case of employing these other diols, a random polycondensationmay be carried out.

The molar ratio of the diol with respect to the dicarboxylic acid in theraw materials is not particularly restricted. It preferably ranges from1.0 to 2.0, and more preferably ranges from 1.1 to 1.5.

The temperature during production of the polyester polyol is notparticularly restricted. It preferably ranges from 100 to 300° C., andmore preferably ranges from 150 to 250° C.

The number average molecular weight of the polyester polyol preferablyranges from 400 to 8,000, and more preferably ranges from 600 to 5,000.

In addition, it is preferable that the polyester polyol be producedwithout employing solvents. However, solvents which are inert withrespect to the reaction may be employed, and for example, ketones suchas methyl ethyl ketone, methyl isobutyl ketone, or the like, ethers suchas tetrahydrofuran or the like, aromatic hydrocarbons such as benzene,toluene, xylene, or the like may be employed.

(2) Preparation of the Urethane Prepolymer and Neutralization of theSame:

As a raw material for a urethane prepolymer, a mixture produced bymixing, in a polyester polyol which is a raw material for the urethaneprepolymer, other kinds of polyols such as a polycarbonate polyol, apolyether polyol, or the like may be employed. In this case, the ratioof the polyester polyol employed to the total of the polyols ispreferably from 50% by weight or more, and more preferably is from 70%by weight or more.

Examples of the compounds having an acidic group include compounds whichhave an acidic group such as a carboxyl group, a sulfonic group, aphosphono group, or the like, and preferably have a carboxyl group, in amolecule, and have two or more groups having an activated hydrogencapable of reacting with an isocyanate group, such as a hydroxyl groupor the like in a molecule.

Thus, examples of the compounds having an acidic group includedimethylol alkanoic acids such as dimethylol propionic acid, dimethylolbutanoic acid, dimethylol pentanoic acid, dimethylol heptanoic acid,dimethylol octanoic acid, and the like,N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid, reaction products ofsulfoisophthalic acid and a multi-functional hydroxy compound, areaction product of 2,3-epoxypropanol and mono-2-ethylhexyl phosphate,2,3-dihydroxypropyloctyl phosphate, and the like. Among these,dimethylol alkanoic acids such as dimethylol propionic acid, dimethylolbutanoic acid, dimethylol pentanoic acid, dimethylol heptanoic acid,dimethylol octanoic acid, and the like are preferable.

Compounds having an acidic group are preferably employed so that theacid value of the polyurethane which is the final desired product rangesfrom 0.1 to 100 mg KOH/g, and more preferably so that it ranges from 5to 40 mg KOH/g.

Examples of the polyisocyanates include compounds having two or moreisocyanate groups, for example, aromatic diisocyanates such asdiphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylenediisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate,2,4-naphthalene diisocyanate, 1,5-naphthalene diisocyanate, p-xylylenediisocyanate, and the like; alicyclic diisocyanates such as isophoronediisocyanate, 4,4′-diisocyanate dicyclohexane, 4,4′-diisocyanatedicyclohexylmethane, and the like; aliphatic diisocyanates such ashexamethylene diisocyanate, tetramethylene diisocyanate, and the like;and so on. They may be employed alone or in combination with two or moreof the same.

Polyisocyanates are preferably employed so that the molar ratio of anisocyanate group to a hydroxyl group in the raw materials ranges from1.1 to 10.0, and more preferably so that the ratio ranges from 1.5 to5.0.

The reaction temperature in the urethane forming reaction preferablyranges from 20 to 150° C., and more preferably ranges from 40 to 120° C.

In addition, the urethane forming reaction maybe carried out withoutemploying reaction solvents. It may also be carried out in a reactionsolvent such as methyl ethyl ketone, methyl isobutyl ketone,tetrahydrofuran, 1,4-dioxane, ethyl acetate, toluene, xylene, acetone,dimethylformamide, or the like, if necessary.

In addition, during the urethane forming reaction, an organometalliccatalyst such as tin octylate or the like or a urethane formingcatalyst, for example, a tertiary amine such as triethylene diamine orthe like maybe employed, if necessary. The amount of the catalyst is ina range of 0.05 to 5% by weight with respect to the reaction mixture.

The neutralization of the acidic group in the urethane prepolymer usinga basic compound can be carried out by adding the basic compound to theurethane prepolymer. Furthermore, commonly, water is added to theneutralized urethane prepolymer to dissolve or disperse the urethaneprepolymer in water. Alternatively, water can be added to the urethaneprepolymer, followed by neutralization. However, it is preferable thatwater be added to the neutralized urethane prepolymer.

The basic compounds for use in neutralization are preferably employed inan amount of 0.5 to 1.5 equivalents with respect to the acid groups inthe urethane prepolymer, and more preferably in an amount of 0.8 to 1.2equivalents.

In addition, as the basic compounds, any compounds capable ofneutralizing the acidic group and forming a salt can be employed.Examples of the basic compounds include ammonia, organic amines such astriethylamine, ethylene diamine, propylamine, dibutylamine, amylamine,1-aminooctane, 2-dimethylaminoethanol, ethylaminoethanol,2-diethylaminoethanol, 1-amino-2-propanol, 2-amino-1-propanol,3-amino-1-propanol, 1-dimethylamino-2-propanol,3-dimethylamino-1-propanol, 2-propylaminoethanol, ethoxypropylamine,aminobenzyl alcohol, morpholine, and the like, hydroxides or carbonatesof an alkali metal or an alkaline earth metal, such as sodium hydroxide,potassium hydroxide, sodium carbonate, potassium carbonate, and thelike. Among these, organic amines are preferably employed.

After neutralization by using the basic compound, the urethaneprepolymer may be emulsified, if necessary. In this case, an emulsifiermay be employed in an amount of 0.1 to 5 parts by weight with respect tothe urethane prepolymer. Examples of the emulsifiers include anionicsurfactants, nonionic surfactants, polymer emulsifiers, and the like.Examples of the anionic surfactants include higher alcohol sulfates,alkyl benzene sulfates, polyoxyethylene alkyl sulfates, polyoxyethylenealkyl phenol ether sulfates, and the like. Examples of the nonionicsurfactants include polyoxyethylene alkyl phenol ethers, ethylene oxidepropylene oxide block polymers, sorbitan derivatives, and the like. Inaddition, examples of the polymer emulsifiers include a polyvinylalcohol, hydroxyethylcellulose, and the like.

(3) Preparation of the Polyurethane:

In order to make the urethane prepolymer into the polymer with a highmolecular weight, the prepolymer is subjected to a reaction with achain-elongation agent, thus producing a polyurethane according to thepresent invention. As the chain-elongation agent in this case, diamines,polyols, alkanolamines, hydrazine, or the like, having a low molecularweight, are employed.

Examples of the diamines include ethylenediamine, propylenediamine,tetramethylenediamine, hexamethylenediamine, isophoronediamine,1,4-cyclohexanediamine, and the like.

Examples of the polyols include ethylene glycol, propylene glycol,1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, hydroquinone, and thelike.

Examples of the alkanolamines include diethanolamine, triethanolamine,and the like.

The chain-elongation agents are preferably employed so that the molarratio of the isocyanate groups in the urethane prepolymer to thehydroxyl groups or amino groups in the chain-elongation agent rangesfrom 0.1 to 10, and more preferably so that it ranges from 0.7 to 1.5.

The reaction between the urethane prepolymer and the chain-elongationagent is commonly carried out at 20 to 100° C., and preferably at 20 to50° C.

In addition, the polyurethanes according to the present inventioninclude the urethane prepolymers prepared in the above step (2), inaddition to the polyurethanes prepared in the above step (3).

As the aqueous polyurethane resins comprising the polyurethane, thosewherein the polyurethane prepared as described above is dissolved ordispersed in water may be given. Examples of methods for dissolving ordispersing the polyurethane in water include a method wherein a urethaneprepolymer is prepared, followed by addition of water and an emulsifieror the like if necessary (and furthermore, a reaction with achain-elongation agent, thus forming a polyurethane). Alternatively,after preparation of the polyurethane, water and an emulsifier or thelike if necessary may be added thereto to dissolve or disperse it inwater.

The amount of the solid materials in the aqueous polyurethane resinsaccording to the present invention is not particularly restricted, anddepends on the uses of the same. It preferably ranges from 30 to 70% byweight.

In addition, for the case where a reaction solvent is employed during aurethane forming reaction or the like, the reaction solvent may beremoved after preparation of the polyurethane. Examples of methods forremoving the reaction solvent include a method of removing the solventunder reduced pressure at the temperature not higher than that of theboiling point of water, a method of removing the solvent by employing anitrogen gas or air as a carrier gas, or the like.

The aqueous polyurethane resins according to the present inventionexhibit a superior adhesive property, bonding property, weatherresistance, water resistance, and the like. For this reason, they areuseful for use in coating materials, adhesives, binders, inks, or thelike.

In addition, for the case of employing the aqueous polyurethane resinsfor the uses described above, antioxidants, UV stabilizers, coloringagents, antifoaming agents, fluid adjustors, water repelling agents,agents for imparting lubrication, fillers, or the like may be added tothe aqueous polyurethane resins of the present invention, if necessary.

For the case where the aqueous polyurethane resins of the presentinvention are employed in coating materials, as the coating methods,common methods such as brush coating, spray coating, or the like can beemployed, and the hardening condition may be selected from a broad rangeof drying conditions from drying at ambient temperature to drying withheating. In addition, examples of the materials to be coated includepaper, leather, glass, metal, wood, plastics, inorganic raw materials,concrete, asphalt, and the like. The aqueous polyurethane resins of thepresent invention may be employed as a primer coating agent, an overcoating agent, a one-coat finishing agent, or the like. In addition,other resins such as acrylic resins, polyester resins, epoxy resins,silicone resins, fluorine resins, or the like may be added thereto, ifnecessary.

In addition, for the case where the aqueous polyurethane resins of thepresent invention are employed for use in adhesives, the hardeningcondition may be selected from a broad range of drying conditions fromdrying at ambient temperature to drying with heating. In addition,examples of the materials to be adhered include paper, leather, glass,metal, wood, plastics, inorganic raw materials, concrete, asphalt, andthe like.

Furthermore, the aqueous polyurethane resins according to the presentinvention may be employed for various uses as they are, or may beemployed as a two-liquid type composition with a crosslinking agent, ifnecessary.

Examples of the crosslinking agents include aqueous-type polyisocyanatecrosslinking agents (compounds prepared by reacting an isocyanulate suchas hexamethylene diisocyanate with a polyhydric alcohol such aspolyethylene glycol, or the like; and so on), melamine crosslinkingagents (methoxylated methylol melamine and the like), epoxy crosslinkingagents (ethylene glycol diglycidyl ether and the like), and the like.The amount of the same is not particularly restricted. The crosslinkingagents are preferably employed in an amount of 1 to 40% by weight withrespect to the solid materials in the aqueous polyurethane resins.

In the following, Reference Examples, Examples, Comparative Examples,and Test Examples are described.

BEST MODES FOR CARRYING OUT THE INVENTION REFERENCE EXAMPLE 1 Synthesisof a Polyester Polyol (PEPO) Employing 2,4-diethyl-1,5-pentanediol as aRaw Material

In a flask, 5 mol (730 g) of adipic acid and 7.5 mol (1202 g) of2,4-diethyl-1,5-pentanediol were charged, and were stirred at 500 to 600rpm and mixed at 200 to 220° C. under a nitrogen atmosphere. While theproduced water was removed, a gradual pressure reduction was startedwhen the acid value reached 5 mg KOH/g or less, and was continued untilthe pressure was 0.4 to 0.65 kPa. Furthermore, when the acid valuereached 0.2 mg KOH/g or less and a predetermined hydroxyl group valuewas obtained at 220° C., stirring was stopped. The mixture was recoveredin a vessel, followed by cooling to room temperature, thus producing thedesired polyester polyol (PEPO 1).

REFERENCE EXAMPLE 2 Synthesis of a Polyester Polyol Employing3-methyl-1,5-pentanediol as a Raw Material

The procedures similar to those described in Reference Example 1 werecarried out, except that 3-methyl-1,5-pentanediol was employed insteadof 2,4-diethyl-1,5-pentanediol, thus producing the desired polyesterpolyol (PEPO 2).

REFERENCE EXAMPLE 3 Synthesis of a Polyester Polyol Employing1,4-butanediol as a Raw Material

The procedures similar to those described in Reference Example 1 werecarried out, except that 1,4-butanediol was employed instead of2,4-diethyl-1,5-pentanediol, thus producing the desired polyester polyol(PEPO 3).

The values of the molecular characteristics of the PEPOs produced inReference Examples 1 to 3 are shown in Table 1. Herein, the numberaverage molecular weight (Mn) of each of the PEPOs was calculatedaccording to the equation described below from the hydroxyl group value[OHV (mg KOH/g)] (an end group quantitative method).

Mn=1/(OHV/1000/56.1/2)

Mn: number average molecular weight

OHV: hydroxyl group value

TABLE 1 Molecular characteristics of PEPOs according to ReferenceExamples 1 to 3 PEPO Diol employed Mn PEPO 1 2,4-diethyl-1,5-pentanediol1989 PEPO 2 3-methyl-1,5-pentanediol 2400 PEPO 3 1,4-butanediol 1972

EXAMPLE 1 Syntheses of a Urethane Prepolymer and an Aqueous PolyurethaneResin

In a separable flask of 1L volume, 165.4 g of PEPO 1 and 16.9 g ofdimethylol butanoic acid (DMBA) were charged. The mixture was heated to80° C. while being stirred under a nitrogen atmosphere. The mixture wasfurther stirred for 30 minutes while exhaust was carried out by means ofa vacuum pump at the same time that nitrogen is provided in the flask.After exhaust by means of the vacuum pump was stopped, the temperaturein the flask was lowered to 60° C. Subsequently, 60 g of acetone wasadded thereto. The temperature was again raised to 80° C., andsubsequently, 117.8 g of isophorone diisocyanate (IPDI) was dropwiseadded thereto over one hour. After completion of adding the drops, thetemperature in the flask was maintained at 80° C., and stirring wascontinued until the conversion of the hydroxyl group in the reactionmixture reached 95% or more. Subsequently, the reaction mixture wascooled to 60° C., and 11.6 g of triethylamine was added thereto toneutralize the carboxyl group in the urethane prepolymer, thus producingthe urethane prepolymer.

The conversion of the hydroxyl group in the reaction mixture describedabove was calculated according to the following equation.

Conversion of the hydroxyl group in the reaction mixture=(1−A/B)×100(%)

A: the number of unreacted hydroxyl groups in the reaction mixture

B: the number of hydroxyl groups in the raw material

In a flask, 300 g of the produced urethane prepolymer was charged.Distilled water in an amount of 388 g was portionwise added theretowhile being stirred at 3000 to 4000 rpm by means of a homomixer, thusproducing an aqueous dispersion of the urethane prepolymer. Whilestirring by means of the homomixer was continued, 16.1 g ofethylenediamine (EDA) was added to the aqueous dispersion, thusproducing the desired aqueous polyurethane resin. The ratio of the solidmaterials in the above aqueous polyurethane resin was 50.1% by weight,and the viscosity of the same was 480 mPa·s. The ratio of the solidmaterials was calculated by the following method.

(Method for Calculating the Ratio of the Solid Materials in the AqueousPolyurethane Resin)

An aqueous polyurethane resin was weighed in an amount of about 1 g. Theaqueous polyurethane resin was heated for 2 hours at 105° C. at ambientpressure, and subsequently, the weight of the residue was weighed. Theratio of the solid materials in the aqueous polyurethane resin wascalculated according to the following equation.

Ratio of solid materials=C/D×100(%)

C: weight of the aqueous polyurethane resin after heating

D: weight of the aqueous polyurethane resin before heating

EXAMPLES 2 AND 3 AND COMPARATIVE EXAMPLES 1 TO 3

The desired aqueous polyurethane resins were produced by carrying outthe procedures similar to those described in Example 1 employing the rawmaterials shown in Tables 2-1 and 2-2.

In Table 2-1, PTG1000 is a product produced by Hodogaya Chemical Co.,Ltd. (polyether polyol having Mn=996), and DMPA represents dimethylolpropionic acid.

In Table 3, physical properties of the aqueous polyurethane resinsproduced in each of the Examples and the Comparative Examples are shown.

TABLE 2-1 Copositions of raw materials for aqueous polyurethane resins(1) Compound having an acidic group Amount Amount Resin PEPO added addedacid Kind (g) Kind (g) value Example 1 PEPO 1 165.4 DMBA 16.9 20 Example2 PEPO 1 166.3 DMPA 15.4 20 Example 3 PEPO 1 152.0 DMBA 25.2 30Comparative PEPO 2 179.2 DMBA 15.1 20 Example 1 Comparative PEPO 3 164.8DMBA 16.9 20 Example 2 Comparative PTG1000 120.6 DMBA 17.9 20 Example 3

Unit of the resin acid value is mg KOH/g.

TABLE 2-2 Compositions of raw materials for aqueous polyurethane resins(2) Distilled EDA IPDI water Amount Amount Amount added (g) added (g)added (g) Example 1 16.1 117.8 388.3 Example 2 16.5 118.4 419.8 Example3 15.3 122.8 521.5 Comparative 16.9 105.7 380.7 Example 1 Comparative16.0 118.3 431.6 Example 2 Comparative 21.5 161.5 411.8 Example 3

TABLE 3 Physical properties of aqueous polyurethanes Ratio of solidViscosity materials (%) (mPa · s) pH Example 1 50.1 480 8.9 Example 253.7 1800 9.2 Example 3 37.7 1230 9.8 Comparative 52.0 340 9.8 Example 1Comparative 55.8 470 9.1 Example 2 Comparative 56.9 690 9.1 Example 3

TEST EXAMPLE 1 Evaluation of Aqueous Polyurethane Resins

(1) Preparation of a Polyurethane Film

The films for use in measurements of tensile strength and hydrolysisresistance tests were prepared by coating the aqueous polyurethaneresins produced in Examples 1, 3, or Comparative Examples 1 to 3 on aglass plate so that the thickness of the film was about 300 μm.

(2) Hydrolysis Resistance Test

The test pieces of the polyurethane film were immersed in hot water at60° C. for 4 days. Subsequently, the tensile strength of the same wasmeasured. The value of hydrolysis resistance was calculated according tothe following equation.

Hydrolysis resistance=E/F×100(%)

E: tensile strength after testing

F: tensile strength before testing

The measurement of the tensile strength was carried out according toJISK 7311.

(3) Adhesive Test

An adhesive test was carried out according to JISK 6804. As the materialto be adhered, a birch material (30×25×10 mm) was selected. On anadhesive part of 25×25 mm, 0.125 g of the aqueous polyurethane resin wasuniformly coated, and another birch material wherein no aqueouspolyurethane resins were applied was adhered thereon. Immediately afterthat, adherence between them was secured by means of a rubber band.Subsequently, they were maintained in this state for 24 hours at 23° C.Forty-eight hours after the rubber band was removed, the compressiveshear strength of the same was measured by means of an Autograph AG-1000produced by Shimadzu Corporation.

The results of Test Example 1 are shown in Table 4.

TABLE 4 Evaluation results of polyurethane films Hydrolysis Adhesiveresistance (%) strength (MPa) Example 1 102 8.9 Example 3 94 8.1Comparative 87 5.8 Example 1 Comparative 78 7.6 Example 2 Comparative 883.7 Example 3

From Table 4, it is apparent that the polyurethane resins according tothe present invention exhibit a superior water resistance and adhesiveproperty.

Industrial Applicability

According to the present invention, aqueous polyurethane resins areprovided which exhibit a superior adhesive property, bonding property,weather resistance, water resistance, and the like, and thepolyurethanes for use in these resins.

What is claimed is:
 1. A polyurethane comprising in a molecule: anacidic group which is neutralized by a basic compound; and a structuralunit represented by general formula (I):

(in the formula, R¹ and R² are identical or different, and represent alower alkyl group).
 2. The polyurethane according to claim 1, whereinthe acidic group is a carboxyl group, a sulfo group, or a phosphonogroup.
 3. The polyurethane according to claim 1, wherein the acidicgroup is a carboxyl group.
 4. The polyurethane according to claim 1,wherein the basic compound is a hydroxide or a carbonate of an alkalimetal or an alkaline earth metal, or an organic amine.
 5. An aqueouspolyurethane resin comprising the polyurethane according to any one ofclaims 1 to
 4. 6. The aqueous polyurethane resin according to claim 5,wherein a weight of solid materials is 30 to 70% by weight.
 7. A coatingmaterial comprising the aqueous polyurethane resin according to claim 5.8. An adhesive comprising the aqueous polyurethane resin according toclaim 5.